Glucose counterregulation in man

Hormonal signals, specifically glucagon and epinephrine, are the critical factors in recovery from hypoglycemia, and available evidence is compatible with a central role for these hormones in nonhypoglycemic glucose counterregulation (the prevention of hypoglycemia) as well, although the latter has not been full defined. Obviously, this does not exclude permissive roles for other hormones, such as cortisol and growth hormone, nor does it exclude facilitative roles for neural and/or autoregulatory mechanisms. It should be emphasized that the quantitative contribution of each of these mechanisms to maintenance of the fasting plasma glucose concentration remains to be determined. The mechanisms of hypoglycemic glucose counterregulation in patients with diabetes mellitus have not been systematically defined. However, increments in plasma epinephrine, norephrine, growth hormone, and cortisol occur wit physiologic as well as hypoglycemic decrements in plasma glucose in such patients. The model of normal hypoglycemic glucose counterregulation discussed in this review provides a conceptual basis for plausible, testable hypotheses concerning the mechanisms of hypoglycemic glucose counterregulation in patients with diabetes and those of nonhypoglycemic glucose counterregulation in diabetics and nondiabetics.